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Duchenne muscular dystrophy (DMD). Philip Ord Isaac Lalich. A patient with Duchenne muscular dystrophy. Introduction. Characteristics Weakness Swollen Calve Muscles Strange Gait Muscle Wasting Loss of Ambulation Respiratory Insufficiency Scoliosis Cardiomyopathy (Some Cases ).
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Duchenne muscular dystrophy (DMD) Philip Ord Isaac Lalich
Introduction • Characteristics • Weakness • Swollen Calve Muscles • Strange Gait • Muscle Wasting • Loss of Ambulation • Respiratory Insufficiency • Scoliosis • Cardiomyopathy (Some Cases) • A Type of Muscular Dystrophy • Categorized Under Neuromuscular Diseases • Most Common form of Muscular Dystrophy • Affects 1:3500 Males • 45,000 in U.S • 996,000 Worldwide • Diagnosed with Blood Test or Biopsy
Genetic information • Dystrophin Gene • Locus: Xp21 • X-Linked Recessive • Mutation Types • Point Mutation Frameshift Massive Missense • Premature Stop Codon (Nonsense) • Large Deletion • Location of Mutation Correlates with Severity • Extremely Large Gene • 24 KB 3,685 AA
Molecular description • Structural Protein • Links Actin to the Extra-Cellular Matrix • Gives Cell Rigidity • Cell is Destroyed with Muscle Contraction • Muscle Cells Stop Regenerating
Brief history • (1836) • Meryon (1852) • GuillameDuchenne (1868) • DMD is a severe disease, patients pass in their late 20s to early 30s. • However medical science is making leaps and bounds.
Clinical consequences • Overall skeletal muscle deterioration. • Use of an electric wheelchair. • Some patients develop cardiomyopathy. • Scoliosis due to weakened back and trunk muscles. • Osteoporosis due to lack of weight bearing. • Muscle atrophy. • Respiratory insufficiency: eventual need for ventilator. • Prone to respiratory infection. Retrieved from: http://www.thesundaytimes.co.uk/sto/news/uk_news/Health/article646534.ece
Treatment • Corticosteroid Therapy • Prednisone • Deflazacourt • Side Effects Severe • Weight Gain • Cushinoid Appearance • Emotional Issues • Delayed Puberty • Stunted Growth • Cataracts • Osteoporosis
RESEARCH • Exon Skipping • Antisense oligonucleotides (AONs) interact with splicing machinery. • Diseased exon spliced out with neighboring introns, restores reading frame. • Upregulation of Utrophin • Utrophin is a protein very homologous to dystrophin. • Telomere Exhaustion • Myoblasts run out of telomere length, can’t replace damaged muscle. • Treatment with telomerases may be in order. • Introduction of Myoblasts • Allow gene complementation with healthy dystrophin. • But can trigger immune response. • Gene Replacement • Large gene makes it difficult. • Mini-dystrophin in viral vector. • Stop Codon Suppression • Use of aminoglycoside antibiotics. • Promotes read-through of premature stop codons.
References • Bianchi, M., Biggar, D., Bushby, K., Rogol, A., Rutter, M., & Tseng, B. (2011). Endocrine aspects of Duchenne muscular dystrophy. Neuromuscular Disorders: NMD, 21(4), 298-303. • Bianchi, M., Mazzanti, A., Galbiati, E., Saraifoger, S., Dubini, A., Cornelio, F., & Morandi, L. (2003). Bone mineral density and bone metabolism in Duchenne muscular dystrophy. Osteoporosis International, 14(9), 761-767. • Fairclough, R., Bareja, A., & Davies, K. (2011). Progress in therapy for Duchenne muscular dystrophy. Experimental Physiology, 96(11), 1101-1113. • Guglieri, M., & Bushby, K. (2010). Molecular treatments in Duchenne muscular dystrophy. Current Opinion In Pharmacology, 10(3), 331-337. • Hoffman, E., Brown, R., & Kunkel, L. (1987). Dystrophin: the protein product of the Duchennemuscular dystrophy locus. Cell, 51(6), 919-928. • Pradhan, S., Ghosh, D., Srivastava, N., Kumar, A., Mittal, B., Pandey, C., & Singh, U. (2006). Prednisolone in Duchenne muscular dystrophy with imminent loss of ambulation. Journal Of Neurology, 253(10), 1309-1316. • Sacco, A., Mourkioti, F., Tran, R., Choi, J., Llewellyn, M., Kraft, P., Shkreli, M., Delp, S., Pomerantz, J., Artandi, S., & Blau, M. (2010). Short teleomeres and stem cell exhaustion model Duchenne muscular dystrophy in mdx/mTR mice. Cell, 147(7), 1059-1071. • Sussman, M. (2002). Duchenne muscular dystrophy. The Journal Of The American Academy Of OrthopaedicSurgeons, 10(2), 138-151.